<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="UTF-8" />
    <title></title>
    <style type="text/css">
      * {
        padding: 0;
        margin: 0;
        list-style: none;
        border: 0;
      }

      .all {
        width: 500px;
        height: 200px;
        padding: 7px;
        border: 1px solid #ccc;
        margin: 100px auto;
        position: relative;
      }

      .screen {
        width: 500px;
        height: 200px;
        /* overflow: hidden; */
        position: relative;
      }

      .screen li {
        width: 500px;
        height: 200px;
        overflow: hidden;
        float: left;
      }

      .screen ul {
        position: absolute;
        left: 0;
        top: 0px;
        width: 3000px;
      }

      .all ol {
        position: absolute;
        right: 10px;
        bottom: 10px;
        line-height: 20px;
        text-align: center;
      }

      .all ol li {
        float: left;
        width: 20px;
        height: 20px;
        background: #fff;
        border: 1px solid #ccc;
        margin-left: 10px;
        cursor: pointer;
      }

      .all ol li.current {
        background: yellow;
      }

      #arr {
        display: none;
        z-index: 1000;
      }

      #arr span {
        width: 40px;
        height: 40px;
        position: absolute;
        left: 5px;
        top: 50%;
        margin-top: -20px;
        background: #000;
        cursor: pointer;
        line-height: 40px;
        text-align: center;
        font-weight: bold;
        font-family: "黑体";
        font-size: 30px;
        color: #fff;
        opacity: 0.3;
        border: 1px solid #fff;
      }

      #arr #right {
        right: 5px;
        left: auto;
      }
    </style>
  </head>

  <body>
    <div class="all" id="box">
      <div class="screen" id="screen">
        <ul id="ul">
          <li><img src="images/wf1.jpg" width="500" height="200" /></li>
          <li><img src="images/wf2.jpg" width="500" height="200" /></li>
          <li><img src="images/wf3.jpg" width="500" height="200" /></li>
          <li><img src="images/wf4.jpg" width="500" height="200" /></li>
          <li><img src="images/wf5.jpg" width="500" height="200" /></li>
        </ul>
        <ol id="ol"></ol>
      </div>
      <div id="arr"><span id="left">&lt;</span><span id="right">&gt;</span></div>
    </div>
    <script>
      // 1.获取ul和ol标签对象
      var ul = document.querySelector('#ul');
      var ol = document.querySelector('#ol');
      // 遍历 ul下面的li对象 通过遍历它确定 ol里面的li
      for(var i = 0;i<ul.children.length;i++) {
        // 创建li
        var li = document.createElement('li');
        li.innerHTML = i + 1;
        // 将创建的li追加到ol标签
        ol.appendChild(li)
        // 给第一个li添加类名 current
        if (i === 0) li.className = 'current'
      }
    </script>
  </body>
</html>
